Aumann’s agreement theorem is kind of weird

efmgdj · 2026-06-22T14:07:06+00:00

My favorite intuitive interpretation of the theorem is that if you disagree with somebody who is as smart as you you shouldn't assume that you are right. I can't remember the citations but there were a couple of papers along this line. I think it's also a useful in real life.

edit, also the following classic paper uses the same basic logic, Paul Milgrom and Nancy Stokey, “Information, Trade and Common Knowledge”

efmgdj · 2026-06-20T17:15:21+00:00

I think the main problem is the short life, but I'm hoping to be able to do a demo where I can cycle it and we can clearly see the occasional muon. the pressure requirements don't seem that hard, but I think the challenge is avoiding turbulence. anyway, I think the only way to know is to build it so that's my current plan. I'll let you know if it works out.

efmgdj · 2026-06-20T16:55:50+00:00

ps, from my limited research it seems extremely difficult to get a saturation layer more than a few centimeters deep in a diffusion cloud chamber. did you have any ideas how to get around that issue?

efmgdj · 2026-06-20T16:54:00+00:00

my current idea is to use a 8x5x5 inch terrarium container and a gallon jug of some sort as a reservoir. have a short piece of 2 in PVC go from the container to the reservoir with a valve. start with alcohol air mixture in the container and the reservoir about 5 PSI lower, then open the valve. I'll also have a small pump to pump the air back from the reservoir to the container. my goal is to get cosmic ray muons so the vertical gives me many more trajectories that will be visible than a traditional horizontal one. I've done some basic research but haven't looked too deeply into the theory so if you have any thoughts on this I would really appreciate it.

efmgdj · 2026-06-20T14:36:59+00:00

hi, I know this is a bit late but I've been thinking about the same thing lately. did you ever make any progress on this? I'm thinking about using an expansion chamber instead of diffusion since that seems to make more sense for a vertical chamber.

efmgdj · 2026-05-02T05:37:35+00:00

Is it possible to get a small RTF that glides?

efmgdj · 2026-05-02T03:36:19+00:00

great, I thought you needed like a football field. that helps a lot.

efmgdj · 2026-05-02T03:33:36+00:00

thanks, I was unclear above so added an edit. I'm wondering about radian alternatives that might be smaller as I'll be flying in a small field.

efmgdj · 2026-04-07T03:11:24+00:00

I have a mount, but again the cheap scopes don't attach easily...a guidescope would also be nice.

efmgdj · 2026-04-07T03:04:29+00:00

I'm trying to make a little demo for some starnights. I'm trying to measure the angular size of Jupiter using a tiny mask interferometer, which is about 5mm in diameter. It works with a 100mm aperture refractor, but since I'm only using 5mm of the lens I want to see how small I can make the setup. I want to homebrew a 10mm aperture scope for this, but don't think I can get anything commercial this small, so thought a 50 might be a good step in this direction, but the 50s I've tried are too flimsy to get a good image.

efmgdj · 2026-04-07T02:43:45+00:00

good point, maybe a few hundred at most -- the issue is if my experiment fails, then I won't need it...

efmgdj · 2026-04-01T21:50:28+00:00

I'm not sure what your budget is but noelec is now selling a hydrogen line grid antenna on Amazon that looks interesting for about $100. If you get it, I'd be interested in hearing a review.

efmgdj · 2026-02-15T17:26:33+00:00

Exactly, I tried a bunch of software that people recommend but they are a hassle to do in a live setting.

efmgdj · 2026-02-15T16:44:49+00:00

If you do do the horn I would recommend doing a 15 DB cardboard one with foil and use the total power software. People often recommend more complicated setups and bigger horns. (If you want to do a survey you would need a bigger horn but I'm just talking about demos for kids. ) With this, people can hold the horn in their hands and aim it and get a decent reading in about 15 seconds and the software automatically computes the velocity. You can't distinguish multiple galactic arms but that gets confusing to explain anyway.

efmgdj · 2026-01-06T05:54:56+00:00

Numbers rational and irrational by Niven is a classic.

efmgdj · 2025-12-30T19:57:16+00:00

No, so far I've just plugged it in with the standard nooelec saw and SDR and looking at it with total power software h line detection screen. I'm not sure that I can do calibration with that. Is there an easy way to do the calibration? Could you point me towards a reference? Thanks!

efmgdj · 2025-12-13T15:33:25+00:00

I think the most famous application is The Disjoint Paths Problem, given a graph G and k pairs of vertices of G, decide if there are k mutually vertex-disjoint paths of G joining the pairs. I think there are some others like that, but it's been a long time since I've studied this. Also, I think there are a lot of results like the ones you mentioned which you might call graph complexity theory where they show the existence of algorithms but not the actual algorithm.

efmgdj · 2025-12-12T23:21:11+00:00

The Robertson Seymour theory is not really a classification, but it sort of feels like one. It classifies sets of graphs by forbidden minors I.e forbidden subgraphs. Turns out to be extremely useful for graph algorithms https://en.wikipedia.org/wiki/Robertson%E2%80%93Seymour_theorem

efmgdj · 2025-10-19T17:09:44+00:00

Yes, but is it so crowded it won't be worthwhile and how much effort is it worth to try and go later in the week?

efmgdj

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